This invention relates to amic acids, cyclic imides and mixtures thereof which contain both diacyl hydrazide functionalities and hindered amine light stabilizing functionalities. The invention also relates to the stabilization of polymers or copolymers against the deleterious effects of heat and/or light by the addition of an effective amount of one or more of the compounds. The invention also relates to the stabilization of polymeric compositions by incorporating the amic acid derivatives into the polymeric composition and then heating the polymeric composition in a melt blending step at a temperature above which cyclization of the amic acid to the cyclic imide occurs.
Synthetic polymers such as polyolefins (e.g., polyethylene and polypropylene), styrenics (e.g., polystyrene, rubber modified polystyrene, ABS, etc.), polyvinyl chloride, polycarbonates, polyesters, and polyphenylene ethers, to name a few, are subject to degradation and discoloration upon exposure to heat and/or light with consequent deterioration of mechanical and other properties.
Various stabilizers have been proposed to inhibit such deterioration. Hindered polyalkylpiperidine compounds have found extensive use in the photostabilization of polyolefins. Hydrazides have been used to prevent deterioration of polyolefins by heat, oxidation or heavy metal contamination. Derivatives of hydrazides are also commercially available for use as polymer stabilizers (See Encyclopedia of Polymer Science and Engineering, 2nd Ed. Vol 2. pp 83-84).
In addition to activity as a stabilizer, commercially useful stabilizer additives must have both excellent compatibility with and/or solubility in the polymeric substrate to be stabilized along with superior resistance to loss from the stabilized composition during processing and end-use application. Many stabilizer additives exhibit limited compatibility in certain substrates and excessive tendency to exude, sublime and/or volatilize during weathering or processing of the stabilized compositions. Therefore, it is highly desirable to provide stabilizers that have a high affinity of compatibility with the polymeric compositions to be stabilized.
Prior to the present invention, the results obtained with the known hindered amine light stabilizers have not been fully satisfactory with all types of manufactured articles, either from a stabilization, compatibility, volatility, exudability or economic viewpoint or combinations thereof. Therefore, further improvement in the field of hindered amine light stabilizers is still desirable.
The hydrazido functionalized polyalkylpiperidine starting materials have good light stabilizing properties but they are water soluble and would be readily leached out of the polymeric compositions to be stabilized if the polymeric compositions came in contact with water, steam, or aqueous solutions. Thus, they are not useful themselves in the stabilization of most polymeric compositions without being derivatized.
Cyclic imides containing polyalkylpiperidine moieties have been prepared by reacting cyclic anhydrides with 4-amino-2,2,6,6-tetramethylpiperidine. The imides were prepared by heating the anhydride and the amine in an autoclave at 200.degree.-230.degree. C. for several hours. No mention was made of the corresponding amic acids but the high temperatures employed were obviously used to cyclize the amic acid to the imide since the amine reacts readily with the anydrides at low temperatures (U.S. Pat. No. 4,356,307).
Amic acids were prepared by reacting cyclic anhydrides with 4-amino-2,6,6,6-tetramethylpiperidine at lower temperatures of 40.degree.-140.degree. C. (U.S. Pat. No. 4,001,181).
Amic acids were obtained by reacting cyclic anhydrides with 4-amino-2,2,5,6,6-polyalkylpiperidines. The amic acids were cyclized to the imides with acetic anhydride (U.S. Pat. No. 4,191,683).
U.S. Pat. No. 3,684,765 discloses phthalimide derivatives of 4-amino-2,2,6,6-tetramethylpiperidine. Canadian Patent No. 1,022,296 discloses phthalimide derivatives of 4-amino-1-ethoxycarbonylmethyl-2,2,6,6-tetramethylpiperidine.
All of the above mentioned prior art compounds were prepared from 4-amino-polyalkylpiperidines. None were prepared from hydrazido functionalized polyalkylpiperidines as in the present invention.